Fill the beaker a quarter of the way with warm water. Very little water is needed.

Place the acrylic chamber on the overhead projector with the watch glass inside.  Use the eyedropper to place few drops of warm water on to the watch glass.  Water about the size of a dime should be sufficient.

If you use a document camera, place the piece of black paper underneath the acrylic chamber to improve the contrast.

If you use an overhead projector, do NOT use the black paper.

Place the glass plate on to the acrylic chamber and switch on the vacuum pump.  After a minute or so, the water will freeze, and the ice will look black.